SCCA Solo D Prepared Miata Build

With the rest of the supplies to clean it in hand, it’s time to get back to it.

I really want to show the Before and After in the same shot. 0000 Steel Wool and WD40 (and some elbow grease) did the business on that crud.

The spindle face got a similar treatment, though it took much less effort. Load up a piece of steel wool with WD40, then turn the motor on and it basically cleans itself.

With the big cleanup done, it’s on to the ol’ “install is reverse of removal.” First the carriage goes on…

Followed by the apron and lead screw.

Then the cross-slide, compound and spindle go back on. She cleaned up fairly well if I say so myself!

The shear pin for the lead screw was pretty well boogered on removal. Thankfully, I had this handy-dandy lathe with which to make myself a new one:

After getting it back together, the cross-slide feed was still really sticky. I thought maybe the feed screw was bent (because it’s super skinny). I took it all apart and everything measured fairly straight, so I dove a little deeper and found that the graduated ring was binding up against the screw’s housing at the same spot on every rotation. If I took the ring off, the handle turned perfectly smooth.

I could make it loose enough to work but then it wouldn’t hold its position, or I could make it tight enough to hold its position and it would be impossible to turn through that rough spot. You can sort of see where it’s interfering here, on that dark ring. I broke out the emery cloth and a fresh can of elbow grease and spent a few minutes knocking it back just enough that it turns nice and freely now.

Next, the tail-stock’s alignment was an unknown quantity, so I wanted to take the time to center it up correctly with the bore of the chuck. Usually you’d use a couple of tapered centers for that, but, well, I don’t have any of those yet. I turned a center from a piece of scrap steel rod, and then used a centering bit in the tail-stock (which also comes to a point) and used those 2 points to get it trammed in. It’s probably not *perfect*, but it’s well within good-enough range.

Before:

After:

Next week, the quick change tool post arrives. I’ll need to make a spacer for that, get the tools aligned, and get some feet made for this thing. After that I’ll…probably… have motivation to clean it’s spot in the shop, and then, at long last, put this thing to work.

I know, I know. It’s not a Miata build, but it is Miata adjacent. I’ve already got some parts I’m looking to turned on it for my car. And it’s an interesting process, so I figured some of y’all might be interested.

I’ve been shopping for a small lathe for the shop for some time now, but kinda had a deal fall in my lap for a used, neglected, Emco 8×20 lathe. A buddy had bought it at a “used tool” auction at his work many years ago, then had a kid (and inherited his grandfather’s lathe that also needs work), so this one was just collecting dust.

Only a moderate sketch factor with the rigging, but I stopped a couple times in the first few miles to cinch the straps down as it settled in place (and secure the rear door that had swung open), and it was fine the rest of the way back home.

And just for fun, I turned Baby’s First Chip just to say I had before the teardown started. Because boy did it need to be gone through.

With a little help from a couple friends, we got it down to my workshop. If you’ve ever seen where my shop is, you know how sketchy THAT was. I backed the trailer down the hill, then used the winch to slowly slide it off the trailer and into the workshop, with someone on each side to steer.

One of the first things I noticed (and was pretty worried by) was the runout on the chuck. Hopefully the entire headstock won’t need to be rebuilt, because I found the most likely culprit: a bunch of swarf built up between the back of the chuck and the lathe’s face plate. Hopefully tidying this up will improve that situation, or else I’m going to have to figure out what’s crooked in the system. The nice thing is that the lathe can be used to true itself up if need be.

Next up was the sticky lever in the quick-change gear box for the power feed for the compound. Apparently they’ve been using grease in this thing instead of machine oil. This…will become a running theme. I let it soak in simple green then oiled it while the machine ran for a few minutes and that freed the lever up to move freely side to side. The lead screw will need to be taken off and THOROUGHLY cleaned, however, as it is caked in fine chips. This too will become a running theme.

My next biggest problem is both the free play and stiction in the cross slide. The free play can be tuned out by adjusting the gibs and the tension on the nut that the adjustment screw rides in, but a lot of the stiction is from old, crusty grease. So, the entire compound / cross slide / top slide and apron are going to come apart to be thoroughly cleaned up. I’m not going for “car show” levels of cleanliness, but I want it to run well even if it’s not the most beautiful belle at the ball. Once again, a ton of crud under the tool post. I actually couldn’t find the witness mark for setting the tool post angle because it was caked in dirt and oil. It should turn much more freely now.

Got the cross slide wheel & screw out. Again, CAKED on grease everywhere I turn (unintentional lathe joke!). To be clear, this isn’t grease as you think of it, just heavily applied. This is stuff that’s been on there for 20 years, dried up and left a thick coating of dry crap that has to be scraped off by a fine pick in many instances.

And finally, the compound comes off the ways. This is the bottom of the compound, where it would slide on the lathe bed. As you can see, some surface rust (not anywhere it actually touches the lathe ways, thankfully), and a lot of old oil & dust and grit that will need to be cleaned off.

With the compound, apron and lead screw off, she’s now pretty stark naked.

Up next was to work on the apron (ie: the gearset that uses the lead screw to run the power feed for the compound, and rides under the compound). This is what greeted me when I took it off. Take a moment to click the picture and zoom in on just how bad it is. The amount of crud caked in the threading half-nuts, the caked on grease (more…). After I’d run it for a while, the handle for the power feed was jammed on and couldn’t be disengaged because of what ended up being a chunk of dried grease getting caught in its working. It was bad.

A bath in the parts washer made almost no difference in the grease on the gear train there. I ended up to have to disassemble the power feed engagement lever and gear assembly and then go through the entire gear train and the lead screw, tooth by tooth, thread by thread, with a pick to actually get the hardened gunk out of the system.

The compound angle was really tough to set earlier. This is what I found between the angle dial that’s pressed onto that arbor, and the tool post.

It was a ton of work, but MAN everything turns smoothly now. It’s such a huge difference. I put the barest whiff of white lithium grease on it per the factory service recommendations, and then it’s maintained afterwards with 140W gear oil.

She still needs work, but we’re getting close. I’ve got the final cleaning supplies (specifically, some 0000 steel wool to clean the ways and gibs) coming in the next day or 2, and a handful of replacement parts and upgrades that should be coming next week.

HAHAHAHAHAHAAAAA!
Man, it’s so good. The adjustments are pretty darn sensitive. We spent the first 6 or so runs dialing out a little bit at a time until we got to the point where the previous spot was better and dialed it back up that notch.
Video won’t show much, but being able to make fine adjustments was a nice change of pace… it went from having to be muscled around the course to finally being able to have soft hands on the wheel.

All in all: if your class allows it, or if you’ve got a street car without PS, this is a great bit of kit 😀

Deech came over to help out with the wiring (which is to say: do the wiring) so that it would actually be done properly.

I decided that as much as possible would go into the switch panel box, just to keep everything out of the weather. The controller was secured to the box, then wired to switched power & ground through the switch box panel. We connected to the rheostat, and we were able to use a pair of unused wires for the clutch pedal switch that were already wired into the switch box (but not used) to carry the power and CANBUS signal to the ECU on the steering column. We tapped into those wires near the column and spliced the connector on.

Before tidying up the wiring completely, we went ahead and did a systems test to make sure everything worked. Much to my surprise (because I worked on it…) it worked properly the first time.

“Like a kid at Christmas” is a pretty accurate descriptor. The fact that the steering turns easily without the lever-arm of the steering wheel attached was astonishing. What else can you say other than it just works, as advertised. I ended up needing to turn it down to about 1/3 power on the rheostat just so that there would be some heft in the steering system, even with the tiny steering wheel.

A proper test is coming up at this weekend’s autocross, where we’ll spend some time tuning it in to where it’s happy on course, and happy-enough everywhere else.

With the column completed, I could get it mounted in the car. Woohoo, it fits! And SOMEHOW, the steering wheel spline size is the same for both the GM and stock columns. My quick release bolted right on.

While tiedown straps are nice and simple, they’re not exactly sturdy enough for keeping a steering column in place, so it’s time to break out the cutting and welding tools.

The Miata and GM column mounts are not parallel, so it took a little creativity to get everything lined up correctly. After a little bit of measuring, I realized I could cut the shapes I needed out of a drop of 2″ square tube. Everything looks parallel in the picture, but there’s about a 1/4″ slope on 1 side of each bracket to fix the difference in angle between the stock pickup and the GM mount.

The stock column mounting-plate made a good datum & base to fabricate from. The brackets are bolted to the GM break-away tabs as they would in the donor vehicle, retaining all of the safety features built in to the new column.

I added a couple gussets to stiffen things up, as there will be a fair deal of torque put on this mount during competition.

I hacked the lower mounts off of the sacrificial column, and used the stock firewall mount points as the basis for the new lower mounts. The left-side mount was by far the most difficult. It took quite a bit of jiggery-pokery to get all of the angles correct so that there was ample clearance for the brake pedal.

There was far more room to work with on the right-hand side.

I’d been working with the motor disconnected, as it is big and heavy, and would make things far more difficult in this stage. The time has come to put it back on. Plenty of clearance in the footwell.

Also, check it! I can get about 1″ of tilt on the column (nearly the full stroke in the mounts)! I was fairly convinced that the tilt wouldn’t work with my install, but here we are. Finally, an NA Miata with the oft-advertised but never before actually seen tilting steering column!

The tilting column adjuster handle is VERY much in the way when climbing around the column getting in and out of the car, so that needed to be modified to tuck it out of the way:

I also went ahead and installed a smaller steering wheel. I went from a ~14″ / 350mm wheel to a 11″ / 280mm wheel. This effectively reduces the arc length that the driver’s hands need to travel to put in the same steering angle by about 25%.

With all of the hardware complete, I could get a start on the electrics. I ran and terminated all of the large-gauge wires that carry power to the motor (that are connected directly to the battery with a 60 amp fuse in line), and started modifying the switch panel to accept the potentiometer. I should be able to put the controller in there as well, to keep it out of the box, and tap into a couple of spare pins in the harness going out of the box to run the controller output to the motor, making for a nice, clean install.

If I have one complaint about the race car it’s that the steering wheel is fairly brutal on the driver. With aero and 9″ slicks going through a Manual rack there’s a ton of feedback. Too much feedback. And because of how heavy it is even with the Manual rack (again, 9″ slicks), I haven’t even wanted to run a depowered PS rack.

Of course, power steering would fix this, but it’s heavy, often messy when they boil over, and saps power from the engine. I already don’t have nearly enough power, so that’s out.

However, I found out recently about a GM electric steering column that’s been seeing heavy use in Rally and other offroad racing disciplines, along with a company that sells a controller that spoofs the CanBus signal, and allows you to adjust the amount of steering assist. I’ve been toying with the idea for a while now, but an autox buddy had one installed in his Ecotec powered Lotus 7 clone and frigging loves it. With some direct experience and some research in the bag, the time came to start building.

So here’s the plan:
-Snag a steering column & controller
-Fabricate mounts and an intermediate “adapter” to go between the end of the GM rack and the input of the Miata’s intermediate shaft. I want to keep it as bolt-in as possible in case something breaks and I need to swap stock parts in.
-De-Power and refurb the PS rack I’ve had sitting on the shelf for ages now waiting for its moment to shine. With the power steering, adding in the faster rack would be good. I’m going to pair this with a smaller steering wheel to lower the distance my hands will need to travel on the wheel for a given angle of input.
-Add steering rack travel limiters to prevent the 15x10s rubbing on the sway-bar in paddock / grid / during big spins.

The steering column in question is out of the Saturn Vue & Chevy Equinox, and is a little over 3″ shorter than the stock NA steering column. I went to the local Pull A Part and snagged one out of the yard, along with the full wiring harness. The nice thing about this column is that they’re built for far heavier cars than what I’m putting it into, so it should be plenty. This system has seen extensive use in the offroad racing community, and I’ve seen them installed in things between ride-on lawnmowers and Unimogs. It appears to be insanely versatile.

To get everything lined up in the right place took a lot of careful measurement. It doesn’t need to be micron-perfect, but within 1/8″ or so is the goal.

The mounts are within an inch or so of where the Miata’s mounts are, so I’ll be able to use the stock upper mounts points (using a modified stock column mount), and will need to re-engineer the lower mounts. The plan is to weld brackets onto a stock upper column mount, and cut the lower mounts off of a sacrificial stock column.

Overall, the GM column is about 3″ shorter than the stock Miata column. This is a good thing as it will allow me to get the steering wheel in a stock location without having to modify the intermediate shaft that runs between the column and rack.

After disassembling the sacrificial stock Miata steering column, I discovered, much to my amazement, that the lower section (where it bolts to the intermediate shaft) is 3/4″ diameter. And just about every aftermarket steering component out there is 3/4″. Due to that size being ubiquitous, EPowerSteering.com sells a 16mm spline to 3/4″ shaft adapter. I’ll use that and a section of the stock steering column to build a small adapter that will spline / bolt onto the bottom of the GM column, and spline / bolt into the stock intermediate shaft.

I took the parts to a buddy’s shop where we cut the stock steering column down to length, and TIG welded the parts together. It could have been MIGed, but with the threads and fine splines, I wanted to avoid spatter at all costs.

After it was welded, I drilled and tapped through the adapter and spline stub to run a bolt to serve as a failsafe in the event the weld breaks, as that weld essentially is a single-point-of-failure in the steering system.

With the column setup complete, it was time to start fabbing the mounts in the car.

The response I got from the setup stand build has been tremendous. Several folks have suggested that they’d like plans be made available so they can build their own set, and that they’d be happy to throw a few bucks my way for the time that went into developing them. I’m staggered, because I thought I’d make a couple sets for buddies and that would be it, and that would be that.

The directions include a materials list, a cut list, some 3D modeling and photographs of the stands.

Chances are that, having built a few sets now, I may have left out a few things that seem intuitive to me just from having done it several times. Let me know if you have any questions and I’ll do my best to answer them.

If you’d like the plans, e-mail me at amaff5@gmail.com and I’ll send a .PDF with the plans.

This is very much a hobby for me, not a business, and these are super useful tools for “us people”. I’d rather more of my racing buddies have access to them than not, so I’m making the plans available for free. Hell, if we had money to burn we’d just spend $2,000 on the commercially available options and be done with it.

That said, I have put a great deal of time and sweat (omg so much sweat you guys) developing these. If you feel that these were worth it and / or want to throw a few bucks in the hat / Tire Fund for the R&D done on these, you can do so here: